The deteriorating underground infrastructure of water, sewer, gas and other pipelines is creating an ever increasing demand for quick and efficient treatment methods and devices. There are generally two approaches to treat this infrastructure; open trench and trenchless repair. Since many of the existing underground infrastructure is located in congested or urban areas, conventional open trench methods cause significant disruption of service.
There are a variety of known trenchless technologies. Slip lining involves inserting a new pipe (typically HDPE) into an existing pipe. The annular space is grouted. The annular space between the host pipe and the liner can be used to carry sewage from laterals until they have been reinstated to the slip liner. Segments are commonly heat fused which provides for a joint-less pipe. Although this method is technically trenchless, excavations are needed at the insertion pit this method is technically trenchless, excavations are needed at the insertion pit and at each lateral location. A further disadvantage of this method is that with the insertion of a liner, there can be significant loss of hydraulic capacity.
Cured-in-place pipe consists of a flexible fabric tube impregnated with a thermosetting resin. The tube is inserted into an existing pipe and injected steam or hot water cures the resin and shapes the tube into the form of the existing pipe. No excavation is needed as the tube can be inserted through an existing manhole and laterals are reinstated robotically. However, the cost of this method is expensive (equal or greater than pipe replacement, and greater than slip lining).
Fold-and-form pipe consists of a preformed polyethylene or polyvinyl chloride pipe formed into a U-shape, that after insertion is expanded by steam or hot water, to fit snuggly against the host pipe. This method is typically used for pipes with a diameter greater than 48″. There is no excavation necessary as the liner can be inserted through an existing manhole, and laterals are reinstated robotically. This method is less costly than the cured-in-place pipe method.
Deform/reform pipe involves the construction of a profiled wall pipe fabricated at the bottom of a manhole, access shaft or man-entry. A PVC strip is pulled through a winding machine which incorporates a series of rollers that form a circular pipe. The pipe is literally wound into the host pipe.
Epoxy spray coating may be used to extend the life of an existing pipe by increasing its strength and protecting it from corrosion or abrasion. Coatings are difficult to apply if infiltration is present, and most coatings cannot be successfully applied to active water leaks or areas where ponding occurs.
Pipe bursting involves working pits and excavations adjacent to manholes. A pipe is fused on site to make a seamless section. The pipe is then fastened to a bursting tool that breaks the existing pipe and compacts the soil. The new pipeline can be of the same or larger diameter. New watertight fittings are installed at every lateral connection. However, lateral connections have to be excavated so there is more surface disruption than with the cured-in-place or fold-and-form methods.
Trenchless technologies, where underground conduits are installed, repaired and modified using robotic methods address the need of efficient rehabilitation without disruption of services caused by excavations. As such, there exist a number of robotic vehicles to conduct trenchless repairs. For example, U.S. Pat. Nos. 5,878,783 and 6,107,795 to Smart discloses a pipeline vehicle for carrying out operations in a gas pipeline such as drilling and welding of a service pipe which branches off from a main pipe. Another robotic device, for use in sewer pipes and capable of grinding off uneven portions or mending cracks, is disclosed in U.S. Pat. No. 6,101,951 to Sigel. A third example of a robotic pipeline vehicle is the one disclosed in U.S. Pat. No. 4,986,314 to Himmler which is capable of carrying a milling tool and other rotating tools such as wire brushes and polishing or metal cutting wheels.
One disadvantage of the robotic devices identified above is that they are incapable of controlled, small radius turns to move into lateral subconduits which usually intersect a main pipeline or conduit at a sharp angle. The modular train vehicle described by Smart, although able to negotiate bends in the pipe, is unable to actually enter into the lateral branch lines, or pipe take-offs. The robotic vehicles disclosed by Siegel and Himmler face a similar limitation, i.e. they are restricted to navigating the main conduits only.
Other robotic vehicles are capable of small radius turns into intersecting conduits. For example, U.S. Pat. No. 497,707 to Box discloses robotic vehicle for travel through a conduit or pipe which is able to execute turns and navigate extreme bends. However, this vehicle is slow due to its inchworm-like movement resulting from the repeated inflation and deflation of the bladders and the repeated extension and contractions of the bellow members. Furthermore, to travel through conduits of varying sizes Box's vehicle has to be disassembled and then reassembled into a different sized vehicle; effectively preventing it from navigating into intersecting conduits of smaller diameter.
In addition to the robotic devices, other apparatus and methods have also been developed to assist in the treatment of conduits. For example, U.S. Pat. No. 6,301,414 to Liese et al. discloses a communications cable network for use in a duct or tube system wherein the communications cables are mounted on the walls of the duct or pipe system inside a rigid sheath and attached by numerous fastening elements. By installing communications cables inside underground conduits, such as sewers, the cables can be installed in a simple efficient manner all the way to individual buildings without costly earthwork.
However, using individual fasteners to attach a cable or sheath to the inside of a conduit is associated with a number of disadvantages. Generally the fasteners are hooks or loops which are screwed into the conduit wall. The fastening itself, or corrosion at the interface, can eventually damage the pipe, hooks or loops and are slow to install.
In published German Patent application DE 19701787A1 to Hecht, one method of installing fibre-optic cable is disclosed which includes directing a robotic vehicle to periodically place semi-circular cable supporting clips which expand to engage the inside of a conduit. Another alternate method is to introduce a hose along the conduit and inflate it to sandwich a cable therebetween, the hose being induced to harden once deployed—this is believed to be similar to the cured-in-place process described above. No apparatus is specifically disclosed which is capable of placing the clips or for introducing a hose and cable to a conduit. Further, there is no suggested solution for adapting to laterally intersecting and extending conduits. The prior art may still be associated with disadvantages in both speed and economy.
Ideally, a device designed to navigate underground pipelines and conduits would also be able to extend into smaller diameter intersecting branch lines or conduits, adjust to different diameter size pipes and still navigate quickly for production of high throughput and economy.